The present invention relates to a prepress for paper web in which a web is carried between two wires and pressed to remove water therefrom. The present invention also relates to a method for lubricating a load shoe in a prepress and pressing the load shoe against a backing element situated in opposed relationship to the load shoe.
In the prior art, so-called prepress equipment is known in paper drying in which a separate load shoe is used to press the web running between wires, preferably in conjunction with a vacuum roll. The vacuum roll is a roll provided with a vacuum box in its interior whereby with the aid of a vacuum produced therein, water is drawn off from the web through perforation in the roll shell, and preferably also through separate circumferential grooving. A particular drawback in conventional prepress arrangements has been finding an appropriate operating system for the load shoe. Use of oil as the operating liquid in the operating system of the load shoe necessitates that the arrangement be well housed in order to prevent leakages of oil.
It is a problem in conventional prepress arrangements utilizing oil as the operating liquid that there is the potential for the oil to leak and contaminate lubricating medium applied to lubricate the load shoe of the prepress arrangement vis-a-vis the wire passing thereover and thus the web.